PURPOSE: To maintain the peripheral surface of a re-feed roller to be clean so that the lowering of friction coefficient of the roller is prevented, by making the re-feed roller and a separating sheet opposed together to rotate the re-feed roller so that the separating sheet cleans the roller.

CONSTITUTION: A bi-surface copying machine comprises an intermediate tray 30, a paper feed device including a re-feed roller 27 which is contacted to a transfer medium 19 stored in the intermediate tray 30 and having its copied first surface and then feeds it, and a separating sheet 31 for separating the copied transfer medium 19. The one-surface copied transfer medium 19 passes the re-feed roller 27 which makes in contact with the separating sheet 31 to rotate by one rotation. With this arrangement, toner, paper dust, dirt, etc. which are adhered to the re-feed roller 27 are scraped off by the separating sheet 31 so that a friction coefficient on the roller surface of the re-feed roller 27 is prevented from lowering. In the next process the one surface-copied transfer medium is surely fed with good timing by the re-feed roller 27.